This invention relates generally to the art of dishwashing, and more particularly, to a composition for use within a household automatic dishwasher.
Conventional household automatic dishwashers operate with various wash cycles, all of which require the release of a detergent at an appropriate time during the wash cycle. The detergent is conventionally released from a storage compartment within the door of the automatic dishwasher. The detergent compartment is normally defined by a spring loaded door which at the appropriate time in the wash cycle opens to release the detergent within the compartment to the working volume of the dishwasher.
The household automatic dishwashing detergents which have been conventionally utilized are of granular or powder form and, to a large extent, extremely hygroscopic. The property of being highly hygroscopic has led to many problems within the automatic dishwashing art, both within the wash cycle and during storage of the detergent. The absorption and adsorption of moisture by a granular hygroscopic dishwashing detergent tends to inactivate the chlorine-containing agents, and causes the individual granules to cake and coalesce into larger particles, making the product difficult to dispense and dissolve, frequently ineffective and, in some cases, deleterious to the dishwashing process. This dissolving problem is worsened by energy saving strategies which result in the lowering of water temperatures within household dwellings.
Conventional household dishwashing detergent powders and granules generally require a water temperature of at least 130.degree.-140.degree. F. in order to be dissolved for the washing process; thus setting an absolute minimum water temperature for such products to be useful. In an automatic dishwasher, however, even with water at an appropriate temperature, automatic dishwashing detergents may cake within the detergent compartment prior to release to the wash cycle. Such caking causes difficulty in the formation of an aqueous solution which is necessary for detergent to occur and frequently results in deposition of granular and caked detergent particles upon articles being washed and adverse reaction therewith. Spotting and actual pitting of silverware and aluminum utensils can occur from the deposition of granular products during the wash cycle.
Household automatic dishwashing detergents conventionally contain chlorine bleach in order to remove stains and break down proteinaceous matter. The moisture which causes caking also reduces the chlorine stability particularly if chlorinated cyanurates are utilized in the granular detergent composition. Moisture thus presents a double threat to the efficacy of a granular detergent product.
A further problem brought about by the hygroscopic nature of granular dishwashing detergents is associated with the storage and dispensing thereof. Due to the caking which can result upon exposure to moisture, it is necessary that such hygroscopic detergents be stored in containers comprised of a barrier to moisture permeation. Such barrier packing materials are readily available, but complicate the packaging and dispensing schemes. Even with the utilization of barrier material, however, moisture still contacts the packaged material through the container opening, both during use and storage. This problem is exacerbated by the tendency to store such dishwashing detergents in the highly moist environment beneath a kitchen sink.
Attempts to overcome the shortcomings of granular products have been described in several prior art documents. Some attempts utilize a liquid medium rather than a granular medium for the dishwashing detergent. There is, however, a distinct problem with liquid products when it is attempted to dispense or retain the liquid within the detergent compartment of a household automatic dishwasher.
An additional problem associated with the use of a liquid medium is the presence of several constituents within the liquid medium which have a tendency to react with one another prior to the desired time of use within the wash cycle. For example, the prior art has utilized several different liquid products on an institutional level wherein one liquid product is dispensed into the wash cycle containing a surfactant and a separate distinct liquid product containing a source of chlorine is released into the wash cycle. No such dishwashing capability on a household scale, however, has permitted the use of more than one liquid at a time.
There is described in U.S. Pat. No. 4,226,736 to Bush et al a gelled dishwashing detergent containing a nonionic surfactant. The product disclosed therein, however, requires a minimum yield point in order to maintain the gelled product within the detergent compartment of an automatic dishwasher. The product described therein additionally contains no source of chlorine and thus would have to be utilized with the dual composition approach heretofore utilized on an institutional basis as discussed above.